conditional.c

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/* Authors: Karl MacMillan <[email protected]>
 *      Frank Mayer <[email protected]>
 *
 * Copyright (C) 2003 - 2004 Tresys Technology, LLC
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, version 2.
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/slab.h>

#include "security.h"
#include "conditional.h"

/*
 * cond_evaluate_expr evaluates a conditional expr
 * in reverse polish notation. It returns true (1), false (0),
 * or undefined (-1). Undefined occurs when the expression
 * exceeds the stack depth of COND_EXPR_MAXDEPTH.
 */
static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
{

    struct cond_expr *cur;
    int s[COND_EXPR_MAXDEPTH];
    int sp = -1;

    for (cur = expr; cur; cur = cur->next) {
        switch (cur->expr_type) {
        case COND_BOOL:
            if (sp == (COND_EXPR_MAXDEPTH - 1))
                return -1;
            sp++;
            s[sp] = p->bool_val_to_struct[cur->bool - 1]->state;
            break;
        case COND_NOT:
            if (sp < 0)
                return -1;
            s[sp] = !s[sp];
            break;
        case COND_OR:
            if (sp < 1)
                return -1;
            sp--;
            s[sp] |= s[sp + 1];
            break;
        case COND_AND:
            if (sp < 1)
                return -1;
            sp--;
            s[sp] &= s[sp + 1];
            break;
        case COND_XOR:
            if (sp < 1)
                return -1;
            sp--;
            s[sp] ^= s[sp + 1];
            break;
        case COND_EQ:
            if (sp < 1)
                return -1;
            sp--;
            s[sp] = (s[sp] == s[sp + 1]);
            break;
        case COND_NEQ:
            if (sp < 1)
                return -1;
            sp--;
            s[sp] = (s[sp] != s[sp + 1]);
            break;
        default:
            return -1;
        }
    }
    return s[0];
}

/*
 * evaluate_cond_node evaluates the conditional stored in
 * a struct cond_node and if the result is different than the
 * current state of the node it sets the rules in the true/false
 * list appropriately. If the result of the expression is undefined
 * all of the rules are disabled for safety.
 */
int evaluate_cond_node(struct policydb *p, struct cond_node *node)
{
    int new_state;
    struct cond_av_list *cur;

    new_state = cond_evaluate_expr(p, node->expr);
    if (new_state != node->cur_state) {
        node->cur_state = new_state;
        if (new_state == -1)
            printk(KERN_ERR "SELinux: expression result was undefined - disabling all rules.\n");
        /* turn the rules on or off */
        for (cur = node->true_list; cur; cur = cur->next) {
            if (new_state <= 0)
                cur->node->key.specified &= ~AVTAB_ENABLED;
            else
                cur->node->key.specified |= AVTAB_ENABLED;
        }

        for (cur = node->false_list; cur; cur = cur->next) {
            /* -1 or 1 */
            if (new_state)
                cur->node->key.specified &= ~AVTAB_ENABLED;
            else
                cur->node->key.specified |= AVTAB_ENABLED;
        }
    }
    return 0;
}

int cond_policydb_init(struct policydb *p)
{
    int rc;

    p->bool_val_to_struct = NULL;
    p->cond_list = NULL;

    rc = avtab_init(&p->te_cond_avtab);
    if (rc)
        return rc;

    return 0;
}

static void cond_av_list_destroy(struct cond_av_list *list)
{
    struct cond_av_list *cur, *next;
    for (cur = list; cur; cur = next) {
        next = cur->next;
        /* the avtab_ptr_t node is destroy by the avtab */
        kfree(cur);
    }
}

static void cond_node_destroy(struct cond_node *node)
{
    struct cond_expr *cur_expr, *next_expr;

    for (cur_expr = node->expr; cur_expr; cur_expr = next_expr) {
        next_expr = cur_expr->next;
        kfree(cur_expr);
    }
    cond_av_list_destroy(node->true_list);
    cond_av_list_destroy(node->false_list);
    kfree(node);
}

static void cond_list_destroy(struct cond_node *list)
{
    struct cond_node *next, *cur;

    if (list == NULL)
        return;

    for (cur = list; cur; cur = next) {
        next = cur->next;
        cond_node_destroy(cur);
    }
}

void cond_policydb_destroy(struct policydb *p)
{
    kfree(p->bool_val_to_struct);
    avtab_destroy(&p->te_cond_avtab);
    cond_list_destroy(p->cond_list);
}

int cond_init_bool_indexes(struct policydb *p)
{
    kfree(p->bool_val_to_struct);
    p->bool_val_to_struct =
        kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum *), GFP_KERNEL);
    if (!p->bool_val_to_struct)
        return -ENOMEM;
    return 0;
}

int cond_destroy_bool(void *key, void *datum, void *p)
{
    kfree(key);
    kfree(datum);
    return 0;
}

int cond_index_bool(void *key, void *datum, void *datap)
{
    struct policydb *p;
    struct cond_bool_datum *booldatum;
    struct flex_array *fa;

    booldatum = datum;
    p = datap;

    if (!booldatum->value || booldatum->value > p->p_bools.nprim)
        return -EINVAL;

    fa = p->sym_val_to_name[SYM_BOOLS];
    if (flex_array_put_ptr(fa, booldatum->value - 1, key,
                   GFP_KERNEL | __GFP_ZERO))
        BUG();
    p->bool_val_to_struct[booldatum->value - 1] = booldatum;

    return 0;
}

static int bool_isvalid(struct cond_bool_datum *b)
{
    if (!(b->state == 0 || b->state == 1))
        return 0;
    return 1;
}

int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
{
    char *key = NULL;
    struct cond_bool_datum *booldatum;
    __le32 buf[3];
    u32 len;
    int rc;

    booldatum = kzalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
    if (!booldatum)
        return -ENOMEM;

    rc = next_entry(buf, fp, sizeof buf);
    if (rc)
        goto err;

    booldatum->value = le32_to_cpu(buf[0]);
    booldatum->state = le32_to_cpu(buf[1]);

    rc = -EINVAL;
    if (!bool_isvalid(booldatum))
        goto err;

    len = le32_to_cpu(buf[2]);

    rc = -ENOMEM;
    key = kmalloc(len + 1, GFP_KERNEL);
    if (!key)
        goto err;
    rc = next_entry(key, fp, len);
    if (rc)
        goto err;
    key[len] = '\0';
    rc = hashtab_insert(h, key, booldatum);
    if (rc)
        goto err;

    return 0;
err:
    cond_destroy_bool(key, booldatum, NULL);
    return rc;
}

struct cond_insertf_data {
    struct policydb *p;
    struct cond_av_list *other;
    struct cond_av_list *head;
    struct cond_av_list *tail;
};

static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
{
    struct cond_insertf_data *data = ptr;
    struct policydb *p = data->p;
    struct cond_av_list *other = data->other, *list, *cur;
    struct avtab_node *node_ptr;
    u8 found;
    int rc = -EINVAL;

    /*
     * For type rules we have to make certain there aren't any
     * conflicting rules by searching the te_avtab and the
     * cond_te_avtab.
     */
    if (k->specified & AVTAB_TYPE) {
        if (avtab_search(&p->te_avtab, k)) {
            printk(KERN_ERR "SELinux: type rule already exists outside of a conditional.\n");
            goto err;
        }
        /*
         * If we are reading the false list other will be a pointer to
         * the true list. We can have duplicate entries if there is only
         * 1 other entry and it is in our true list.
         *
         * If we are reading the true list (other == NULL) there shouldn't
         * be any other entries.
         */
        if (other) {
            node_ptr = avtab_search_node(&p->te_cond_avtab, k);
            if (node_ptr) {
                if (avtab_search_node_next(node_ptr, k->specified)) {
                    printk(KERN_ERR "SELinux: too many conflicting type rules.\n");
                    goto err;
                }
                found = 0;
                for (cur = other; cur; cur = cur->next) {
                    if (cur->node == node_ptr) {
                        found = 1;
                        break;
                    }
                }
                if (!found) {
                    printk(KERN_ERR "SELinux: conflicting type rules.\n");
                    goto err;
                }
            }
        } else {
            if (avtab_search(&p->te_cond_avtab, k)) {
                printk(KERN_ERR "SELinux: conflicting type rules when adding type rule for true.\n");
                goto err;
            }
        }
    }

    node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
    if (!node_ptr) {
        printk(KERN_ERR "SELinux: could not insert rule.\n");
        rc = -ENOMEM;
        goto err;
    }

    list = kzalloc(sizeof(struct cond_av_list), GFP_KERNEL);
    if (!list) {
        rc = -ENOMEM;
        goto err;
    }

    list->node = node_ptr;
    if (!data->head)
        data->head = list;
    else
        data->tail->next = list;
    data->tail = list;
    return 0;

err:
    cond_av_list_destroy(data->head);
    data->head = NULL;
    return rc;
}

static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
{
    int i, rc;
    __le32 buf[1];
    u32 len;
    struct cond_insertf_data data;

    *ret_list = NULL;

    len = 0;
    rc = next_entry(buf, fp, sizeof(u32));
    if (rc)
        return rc;

    len = le32_to_cpu(buf[0]);
    if (len == 0)
        return 0;

    data.p = p;
    data.other = other;
    data.head = NULL;
    data.tail = NULL;
    for (i = 0; i < len; i++) {
        rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
                     &data);
        if (rc)
            return rc;
    }

    *ret_list = data.head;
    return 0;
}

static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
{
    if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
        printk(KERN_ERR "SELinux: conditional expressions uses unknown operator.\n");
        return 0;
    }

    if (expr->bool > p->p_bools.nprim) {
        printk(KERN_ERR "SELinux: conditional expressions uses unknown bool.\n");
        return 0;
    }
    return 1;
}

static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
{
    __le32 buf[2];
    u32 len, i;
    int rc;
    struct cond_expr *expr = NULL, *last = NULL;

    rc = next_entry(buf, fp, sizeof(u32));
    if (rc)
        return rc;

    node->cur_state = le32_to_cpu(buf[0]);

    len = 0;
    rc = next_entry(buf, fp, sizeof(u32));
    if (rc)
        return rc;

    /* expr */
    len = le32_to_cpu(buf[0]);

    for (i = 0; i < len; i++) {
        rc = next_entry(buf, fp, sizeof(u32) * 2);
        if (rc)
            goto err;

        rc = -ENOMEM;
        expr = kzalloc(sizeof(struct cond_expr), GFP_KERNEL);
        if (!expr)
            goto err;

        expr->expr_type = le32_to_cpu(buf[0]);
        expr->bool = le32_to_cpu(buf[1]);

        if (!expr_isvalid(p, expr)) {
            rc = -EINVAL;
            kfree(expr);
            goto err;
        }

        if (i == 0)
            node->expr = expr;
        else
            last->next = expr;
        last = expr;
    }

    rc = cond_read_av_list(p, fp, &node->true_list, NULL);
    if (rc)
        goto err;
    rc = cond_read_av_list(p, fp, &node->false_list, node->true_list);
    if (rc)
        goto err;
    return 0;
err:
    cond_node_destroy(node);
    return rc;
}

int cond_read_list(struct policydb *p, void *fp)
{
    struct cond_node *node, *last = NULL;
    __le32 buf[1];
    u32 i, len;
    int rc;

    rc = next_entry(buf, fp, sizeof buf);
    if (rc)
        return rc;

    len = le32_to_cpu(buf[0]);

    rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
    if (rc)
        goto err;

    for (i = 0; i < len; i++) {
        rc = -ENOMEM;
        node = kzalloc(sizeof(struct cond_node), GFP_KERNEL);
        if (!node)
            goto err;

        rc = cond_read_node(p, node, fp);
        if (rc)
            goto err;

        if (i == 0)
            p->cond_list = node;
        else
            last->next = node;
        last = node;
    }
    return 0;
err:
    cond_list_destroy(p->cond_list);
    p->cond_list = NULL;
    return rc;
}

int cond_write_bool(void *vkey, void *datum, void *ptr)
{
    char *key = vkey;
    struct cond_bool_datum *booldatum = datum;
    struct policy_data *pd = ptr;
    void *fp = pd->fp;
    __le32 buf[3];
    u32 len;
    int rc;

    len = strlen(key);
    buf[0] = cpu_to_le32(booldatum->value);
    buf[1] = cpu_to_le32(booldatum->state);
    buf[2] = cpu_to_le32(len);
    rc = put_entry(buf, sizeof(u32), 3, fp);
    if (rc)
        return rc;
    rc = put_entry(key, 1, len, fp);
    if (rc)
        return rc;
    return 0;
}

/*
 * cond_write_cond_av_list doesn't write out the av_list nodes.
 * Instead it writes out the key/value pairs from the avtab. This
 * is necessary because there is no way to uniquely identifying rules
 * in the avtab so it is not possible to associate individual rules
 * in the avtab with a conditional without saving them as part of
 * the conditional. This means that the avtab with the conditional
 * rules will not be saved but will be rebuilt on policy load.
 */
static int cond_write_av_list(struct policydb *p,
                  struct cond_av_list *list, struct policy_file *fp)
{
    __le32 buf[1];
    struct cond_av_list *cur_list;
    u32 len;
    int rc;

    len = 0;
    for (cur_list = list; cur_list != NULL; cur_list = cur_list->next)
        len++;

    buf[0] = cpu_to_le32(len);
    rc = put_entry(buf, sizeof(u32), 1, fp);
    if (rc)
        return rc;

    if (len == 0)
        return 0;

    for (cur_list = list; cur_list != NULL; cur_list = cur_list->next) {
        rc = avtab_write_item(p, cur_list->node, fp);
        if (rc)
            return rc;
    }

    return 0;
}

static int cond_write_node(struct policydb *p, struct cond_node *node,
            struct policy_file *fp)
{
    struct cond_expr *cur_expr;
    __le32 buf[2];
    int rc;
    u32 len = 0;

    buf[0] = cpu_to_le32(node->cur_state);
    rc = put_entry(buf, sizeof(u32), 1, fp);
    if (rc)
        return rc;

    for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next)
        len++;

    buf[0] = cpu_to_le32(len);
    rc = put_entry(buf, sizeof(u32), 1, fp);
    if (rc)
        return rc;

    for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next) {
        buf[0] = cpu_to_le32(cur_expr->expr_type);
        buf[1] = cpu_to_le32(cur_expr->bool);
        rc = put_entry(buf, sizeof(u32), 2, fp);
        if (rc)
            return rc;
    }

    rc = cond_write_av_list(p, node->true_list, fp);
    if (rc)
        return rc;
    rc = cond_write_av_list(p, node->false_list, fp);
    if (rc)
        return rc;

    return 0;
}

int cond_write_list(struct policydb *p, struct cond_node *list, void *fp)
{
    struct cond_node *cur;
    u32 len;
    __le32 buf[1];
    int rc;

    len = 0;
    for (cur = list; cur != NULL; cur = cur->next)
        len++;
    buf[0] = cpu_to_le32(len);
    rc = put_entry(buf, sizeof(u32), 1, fp);
    if (rc)
        return rc;

    for (cur = list; cur != NULL; cur = cur->next) {
        rc = cond_write_node(p, cur, fp);
        if (rc)
            return rc;
    }

    return 0;
}
/* Determine whether additional permissions are granted by the conditional
 * av table, and if so, add them to the result
 */
void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
{
    struct avtab_node *node;

    if (!ctab || !key || !avd)
        return;

    for (node = avtab_search_node(ctab, key); node;
                node = avtab_search_node_next(node, key->specified)) {
        if ((u16)(AVTAB_ALLOWED|AVTAB_ENABLED) ==
            (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
            avd->allowed |= node->datum.data;
        if ((u16)(AVTAB_AUDITDENY|AVTAB_ENABLED) ==
            (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
            /* Since a '0' in an auditdeny mask represents a
             * permission we do NOT want to audit (dontaudit), we use
             * the '&' operand to ensure that all '0's in the mask
             * are retained (much unlike the allow and auditallow cases).
             */
            avd->auditdeny &= node->datum.data;
        if ((u16)(AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
            (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
            avd->auditallow |= node->datum.data;
    }
    return;
}